Electric resistance element.



H. W. DENHARD.

ELECTRIC RESISTANCE ELEMENT.1

APPLICATION FILED OCT. 31.1911.

Patented June 15, 1915.

UNITED STATES PATENT OFFICE.

HARRY W. DENHARD, OF SAN FRANCISCO, CALIFORNIA, ASSIGNOR TO THE CUTLER-HAMMER MFG. (30., OF MILWAUKEE, WISCONSIN, A CORPORATION OF WISCONSIN.

ELECTRIC RESISTANCE ELEMENT.

To all whom it may concern:

Be it known that I, HARRY IV. DENHABD,

a citizen of the United States, residing at San Francisco, in the countyof San Francisco and State of California, have invented new and usefulImprovements in Electric Resistance Elements, of which the following isa full, clear, concise, and exact description, referene being had to theaccompanying drawing, forming a part of this specification.

My invention relates to electric resistance elements.

It is especially adapted for use in connection with electric heatingdevices, such as electric laundry irons, and it is in this connectionthat I shall describe the same in this application. My invention is nothowever, limited in its use to this specific adaptation.

My invention has among its objects to provide an improved electricresistance element which may be manufactured at very small expense andassembled in a very compact form, so that the heat generatedby the sameis distributed in proper proportion to the object to be heated.

A further object of my invention is to provide an improved electricresistance element adapted to use in connection with an electric iron,which is formed of aplurality of strips of resistance material which areso made as to permit them to be assembled in the. form of a unit whichconforms to the shape of an iron and which distributes the heatgenerated in the desired proportion tp the "arious parts of the iron.

Other objects and advantages of my improved construction willhereinafter appear.

In the accompanying drawings I have illustrated one form which myinvention may assume in practice. My invention is not however, limitedto this specific form.

In the view of these drawings :Figure 1 shows av plan view of a blankfrom which the resistance element is formed. Fig. 2 shows a plan view ofan assembled unit. Fig. 3 shows a sectional view of the unit in positionin an iron.

In the construction shown in the drawings, a blank 1, of a resistancematerial, preforabiy metallic, is made up in the form of a strip andpunched as illustrated in Fig. 1. This blank-is preferably slottedthroughout the greater part of its length as at 2, (Fig.

Specification of Letters Patent.

Application filed October 31, 1911.

Patented June 15, 1915.

Serial No. 657,802.

1) in the well known manner and. one side of the same is tapered towarda point near the middle 3, which when the blank is bent into the shapeof a unit, forms the tipof the same. In order that the heat may begreater at the tip of the iron, due to the fact that the heat is morereadily dissipated at the tip, I so arrange the unit that a greater heatdeveloping surface is present at the tip. This I do by bending the blankalong a horizontal line at the point 3, until the two halves of'the samelie in horizontal planes. Since it is unnecessary to heat the back 'ofthe iron, to the high temperature required at the tip, I preferablyleave one end of the blank unslotted, as shown at thedower part of Fig.1.. In order to enable the unit to be held in position in the iron, Ipreferably provide suitable perforations 4, which when the unit isassembled, are arranged concentrically. In order to enable suitableelectric connections to be made, I provide each of the blanks with anextension 5, at one of its ends, which is preferably stamped out withthe blank, and I also preferably provide a perforation 6, at theopposite end, so that the terminals may be connected to the unit as byriveting if desired.

When the unit is assembled it assumes the form shown in Fig. 2, whereinthe two halves of the blank shown in Fi g. 1 are folded upon each otheralong the line 3, so that when the two halves are placed together withtheir straight edges in parallel relation, a unit is formed which willconform to the shape of an iron, in which it is desired to place thesame. When in this position, the lower flap of the blank shown in Fig. 1rests upon the flap shown at the top, and the perforations 4, registerwith each other, while the perforations 6 are brought close together atthe back of the iron. The extensions 5, at the back of the units. areconnected together in any suitable manner as by crimping or if desired,by brazing or welding, so that a complete unitary structure is provided.In order to insulate the parts, the two flaps which are bent over uponeach other mayv be suitably spaced from each other by a sheet ofinsulation 7. If desired I may use mica as this insulation.

In 3, I have shown one manner in which the unit may be placed inposition in an. iron. For purposes of illustration, the

, I-employ mica as this insulation. When placed between these sheets Kof insulation the unit is then placed between the storage plate 9, andthe body portion 10,- of the iron,

' as shown' in Fig.- 3. As usual in such constructions, the plate 9 maybe brought down .very tightly upon the unit by means of suitable screws,or bolts 11 so that the unit is clamped between the surface of the plateand the body portion of the iron. Since this form of clamping. the unitwithin the-iron is well known, I have not illustrated the same in detailin the drawing.

By my improved construction, I am able to produce a unit whichmay bemade up into very thin form, so that it may be brought into intimaterelationwith the sur face to be heated, and thus reduce the amount ofheat lost through radiation or otherwise. Further, by the use of theslotted resistance material, I am able to provide a unit of high heatingcapacity. By my improved means .of arranging the unit, I am able todistribute the heat to the parts of the iron where it ismost needed, andin the desired proportion, so that a practically uni form temperaturemay be. maintained. Further, I am ableto-providean ellicient unit .ofhigh heat developing capacity which may be' manufactured very cheaplyand be readily placed in'position.

While I have, in this application, described one form which my inventionmay assume in practice, my invention may assume other forms than thatshown, and I accordingly wish to cover within the scope of thisapplication all of these forms of my invention falling within itsspirit.

hat I'claim as new and desire to secure by Letters Patent isz 1. Anelectric resistancev unit formed of a pair of strips of slottedresistance ribbon each bent back. on itself to form parallel portions,said portions being of similar shape and conforming to the outline ofthe object to be heated, the lower portion having slots throughout itslength and the upper portion having slots for a portion of its lengthwhereby the maximum quantity .of heat is developed at one end of theunit, the

. adapted to each bent back .onitself to form parallel portions,insulating means between the portions, said portions being ofsimilar-shape and of an area substantially equal to half the area of thebase of the iron, the lower portions of each strip being connected togather electrically at their free-ends and.

slotted throughout their l'en -th, the upper portions of cach'stripbeings otted near the bent-ovcr .end whereby the maximum quantity ofheat is generated atone endjof the un t, the free end of the upperportionsof the strips being adapted to be connected to electricterminals.

- -3. An electriehoating unit having a pair strips of slottcd'resistanceribbon adapted to conform .to the outline of the object to be heated andeach having an area substan tially equal to the areaof one-half of thebase of said object, each of saidstrips havmg a terminal portion whichis bentback on the strip and insulated therefrom, said ter-- minalportions. being slotted adjacent theirbcnt-orer ends whereby the unithas amaX1-' mum heat developing capacity near one-end,

the free ends of said terminal portions being be connected ito anelectr1ccir-- cuit. 4; An electric resistance unit formed of a singlelength. ofslotted-T- resistance J ribbon.

having a body portion and a partiallyslot- 'tcd terminal. portion-bentover-upon one surface of the'body portion andinsulated therefrom,whereby the unit has a maximum heat developing capacity near one end,

the-outline of said terminal portionbeing shaped to coincide with theoutline of said body portion and both conforming to the shape ofthesurface to .be heated.

5. An electric. resistance unit formed of a single length ofslottedresistance ribbon having one'edge of the same tapered toward thecenter of the strip,said strip being tolded substantially at its middleline to form two layers, the end ofone of said layers being leftunslotted. 1

In witness whereof, I have-hereunto subscribed my name in the presenceof two witnesses. Y J e HARRY WFDENHARD. Witnesses: 7

F. L. ROCKWELL, Geo. B. Jones.

